From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Wed, 17 Oct 2018 12:10:39 +0000 (+0100)
Subject: clarify bitwidth
X-Git-Tag: convert-csv-opcode-to-binary~4908
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=3c20bead498f5deaafa031dffde34ecf387f30da;p=libreriscv.git

clarify bitwidth
---

diff --git a/simple_v_extension/specification.mdwn b/simple_v_extension/specification.mdwn
index ec17b082a..fa8eb6b85 100644
--- a/simple_v_extension/specification.mdwn
+++ b/simple_v_extension/specification.mdwn
@@ -1243,9 +1243,19 @@ rd bitwidths).  The pseudo-code is therefore as follows:
         uint64_t l;
     } el_reg_t;
 
+    bw(elwidth):
+        if elwidth == 0:
+            return xlen
+        if elwidth == 1:
+            return xlen / 2
+        if elwidth == 2:
+            return xlen * 2
+        // elwidth == 3:
+        return 8
+
     get_max_elwidth(rs1, rs2):
-        return max(int_csr[rs1].elwidth, # default (XLEN) if not set
-                   int_csr[rs2].elwidth) # again XLEN if no entry
+        return max(bw(int_csr[rs1].elwidth), # default (XLEN) if not set
+                   bw(int_csr[rs2].elwidth)) # again XLEN if no entry
 
     get_polymorphed_reg(reg, bitwidth, offset):
         el_reg_t res;